1. Field of the Invention
This invention relates in general to an error correcting programmable pulse generator, and more particularly to a programmable pulse generator that removes errors due to manufacturing tolerances, power supply variations, and temperature.
2. Description of Related Art
Today""s wireless communications markets are being driven by a multitude of user benefits. Products such as cellular phones, cordless phones, pagers, and the like have freed corporate and individual users from their desks and homes and are driving the demand for additional equipment and systems to increase their utility. As a result digital radio personal communications devices will play an increasingly important role in the overall communications infrastructure in the next decade.
Mixed-signal integration and power management have taken on added importance now that analog and mixed analog-digital ICs have become the fastest-growing segment of the semiconductor industry. Integration strategies for multimedia consoles, cellular telephones and battery-powered portables are being developed, as well as applications for less integrated but highly specialized building blocks that serve multiple markets. These building blocks include pulse generators, data converters, comparators, demodulators, filters, amplifiers and voltage regulators.
One important aspect of electronic devices is the effect of external conditions, such as temperature, imposed on the circuit. In a typical circuit, a voltage can be regulated by controlling its current as a function of the result of the actual voltage output and a predetermined reference voltage. The reference voltage may be constant, but it would be desirable under certain conditions to vary the voltage as a function of temperature or other variables. Nevertheless, there are some key barriers to realizing these desirable conditions.
A large number of integrated circuits are programmable. These circuits are widely used in a variety of programmable devices. Devices such as programmable logic arrays (PAL), integrated fuse logic (IFL), bipolar programmable read only memory (BPROM), erasable programmable read only (EPROM), and other conventional types of circuits require a reference voltage that can vary as a function of temperature, supply and other manufacturing process variations. In a programming process, the integrated circuit programmer must provide a pulse signal that is programmable and will include processes that remove errors due to manuring tolerances, power supply variations, and temperature. Currently this is being accomplished by using different hardware circuits for each logic device. However, this is an uneconomical process.
It can be seen then that there is a need for an error correcting programmable pulse generator that removes errors due to manufacturing tolerances, power supply variation, and temperature.
It can also be seen that there is a need for an error correcting programmable pulse generator that controls amplitude, rise and fall time and the average level of a voltage pulse.
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses error correcting programmable pulse generator that removes errors due to manufacturing tolerances, power supply variation, and temperature.
The present invention solves the above-described problems by providing a programmable pulse generator that controls the amplitude, the rise and fall time and the average level of a signal.
A method in accordance with the principles of the present invention includes generating a signal having a rise and fall time; varying a first and a second impedance to control a rise and fall time and an average level of the signal to produce an output signal, wherein varying the first and the second impedance modifies a first current, a second current and a third current. In addition, simultaneously varying a first reference current to produce a second reference current that is used to generate the first current, the second current and the third current. Further, simultaneously scaling the second reference current to modify the first current, the second current and the third current to offset by the varying of the first and second impedance to reduce errors induced by an external environment, manufacturing tolerances and a changing time constant.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the circuit includes a plurality of registers for scaling the currents.
Another aspect of the present invention is that the controlling of the rise and fall time further includes varying the first and the second impedance to set a time constant, wherein the time constant controls an exponential rise and fall time of the signal.
Another aspect of the present invention is that the varying of the first and the second impedance further includes varying a resistor and a capacitor.
Another aspect of the present invention is that the production of the output signal includes generating a quiescent level when the signal is disabled, wherein the quiescent level is generated by the product of the first current and the first impedance.
Another aspect of the present invention further includes varying a plurality of voltages and a plurality of currents simultaneously.
Another aspect of the present invention is that the first current, second current, and third current are independent of the time constant, a power supply, a manufacturing process, and environmental conditions.
Another aspect of the present invention is that the output signal further includes buffering such that circuits driven by the output do not change the time constant by adding capacitance.
These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.